Alert archive / Virginia / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 340, NWS Baltimore/Washington

August 10, 20214 counties in Virginia

NWS Baltimore/Washington issued this severe thunderstorm warning at Aug 10, 2021, 5:41 PM EDT for 4 counties in Virginia. It was in force for 35 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 10, 2021, 5:41 PM EDT (21:41 UTC)
Expired: Aug 10, 2021, 6:16 PM EDT
In force: 35 min
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon
Damage threat: Considerable
Hail: 1.0 in
Wind: 70.0 mph

Counties Fairfax County, VA, Fauquier County, VA, Loudoun County, VA, Prince William County, VA

The radar

The Sterling radar (KLWX), 6 km from the middle of the area, began a volume at 21:43 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Aug 10, 5:48 PM EDT	TSTM WND DMG	2 Sw Gleedsville, VA	TREES AND BRANCHES DOWN ALONG LIME KILN ROAD.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 9.7 hours before the alert went out and 11 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 529 J/kg
Mixed-layer CIN: -120 J/kg
Mixed-layer LCL: 1096 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 37 m²/s²
0-3 km storm-relative helicity: 65 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

038 
WUUS51 KLWX 102141
SVRLWX
VAC059-061-107-153-102230-
/O.NEW.KLWX.SV.W.0340.210810T2141Z-210810T2230Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
541 PM EDT Tue Aug 10 2021

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southeastern Loudoun County in northern Virginia...
  Northwestern Fairfax County in northern Virginia...
  Northeastern Fauquier County in northern Virginia...
  Northwestern Prince William County in northern Virginia...

* Until 630 PM EDT.

* At 541 PM EDT, severe thunderstorms were located along a line
  extending from near Oatlands to near Middleburg to near The Plains,
  moving east at 25 mph.

  HAZARD...70 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches 
           to fall. This could injure those outdoors, as well as 
           damage homes and vehicles. Roadways may become blocked by 
           downed trees. Localized power outages are possible. 
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Centreville, Reston, Leesburg, South Riding, Herndon, Broadlands,
  Lansdowne, Lowes Island, Brambleton, Dulles International Airport,
  Ashburn, Sterling, Chantilly, Great Falls, Countryside, Arcola,
  Oatlands, Belmont, Gleedsville and Aldie.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3908 7747 3907 7746 3906 7737 3906 7733
      3885 7735 3889 7770 3909 7767 3909 7747
TIME...MOT...LOC 2141Z 273DEG 20KT 3906 7771 3901 7769 3896 7768 3893
7771 3890 7777

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

CJL

2 follow-up statements

244 
WWUS51 KLWX 102156
SVSLWX

Severe Weather Statement
National Weather Service Baltimore MD/Washington DC
556 PM EDT Tue Aug 10 2021

VAC061-153-102206-
/O.CAN.KLWX.SV.W.0340.000000T0000Z-210810T2230Z/
Fauquier VA-Prince William VA-
556 PM EDT Tue Aug 10 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTHEASTERN FAUQUIER AND
NORTHWESTERN PRINCE WILLIAM COUNTIES IS CANCELLED...

The storms which prompted the warning have moved out of the warned 
area. Therefore, the warning has been cancelled.

LAT...LON 3888 7735 3891 7761 3893 7762 3893 7763
      3894 7764 3894 7766 3906 7763 3906 7733
TIME...MOT...LOC 2156Z 268DEG 20KT 3907 7762 3902 7760 3897 7759 3894
7762 3891 7768

$$

VAC059-107-102230-
/O.CON.KLWX.SV.W.0340.000000T0000Z-210810T2230Z/
Loudoun VA-Fairfax VA-
556 PM EDT Tue Aug 10 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 630 PM EDT
FOR SOUTHEASTERN LOUDOUN AND NORTHWESTERN FAIRFAX COUNTIES...

At 556 PM EDT, severe thunderstorms were located along a line
extending from near Leesburg to Oatlands to near Brambleton to near
Arcola to near Middleburg, moving east at 25 mph.

HAZARD...70 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Damaging winds will cause some trees and large branches to 
         fall. This could injure those outdoors, as well as damage 
         homes and vehicles. Roadways may become blocked by downed 
         trees. Localized power outages are possible. Unsecured 
         light objects may become projectiles.

Locations impacted include...
Reston, South Riding, Herndon, Broadlands, Lowes Island, Brambleton,
Dulles International Airport, Ashburn, Sterling, Chantilly, Great
Falls, Countryside, Arcola, Oatlands, Belmont, Gleedsville, Aldie and
Sterling Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3888 7735 3891 7761 3893 7762 3893 7763
      3894 7764 3894 7766 3906 7763 3906 7733
TIME...MOT...LOC 2156Z 268DEG 20KT 3907 7762 3902 7760 3897 7759 3894
7762 3891 7768

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

CJL

069 
WWUS51 KLWX 102216
SVSLWX

Severe Weather Statement
National Weather Service Baltimore MD/Washington DC
616 PM EDT Tue Aug 10 2021

VAC059-107-102226-
/O.CAN.KLWX.SV.W.0340.000000T0000Z-210810T2230Z/
Loudoun VA-Fairfax VA-
616 PM EDT Tue Aug 10 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN LOUDOUN AND
NORTHWESTERN FAIRFAX COUNTIES IS CANCELLED...
    
The storms which prompted the warning have weakened below severe
limits, and have exited the warned area. Therefore, the warning has
been cancelled.

LAT...LON 3888 7735 3891 7761 3893 7762 3893 7763
      3894 7764 3894 7766 3906 7763 3906 7733
TIME...MOT...LOC 2215Z 273DEG 20KT 3906 7748 3901 7746 3896 7745 3893
7748 3890 7754

$$

CJL

The office that day

Everything else NWS Baltimore/Washington issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 10, 1:33 PM EDT	Excessive Heat Watch	LWX	Arlington, Clarke, Fairfax, Fauquier, King George, Loudoun and 6 more	37 hr
Aug 10, 1:33 PM EDT	Heat Advisory	LWX	Arlington, Clarke, Fairfax, Fauquier, King George, Loudoun and 6 more	29 hr
Aug 10, 2:30 PM EDT	Severe Thunderstorm Warning	LWX	Culpeper, Fauquier, Rappahannock	45 min
Aug 10, 2:44 PM EDT	Severe Thunderstorm Warning	LWX	Albemarle, City of Charlottesville	23 min
Aug 10, 3:24 PM EDT	Severe Thunderstorm Warning	LWX	Orange	34 min
Aug 10, 4:15 PM EDT	Severe Thunderstorm Warning	LWX	Fairfax, Prince William, City of Manassas, City of Manassas Park	31 min
Aug 10, 4:34 PM EDT	Severe Thunderstorm Warning	LWX	Fairfax, Loudoun	41 min
Aug 10, 4:42 PM EDT	Severe Thunderstorm Warning	LWX	Culpeper, Fauquier, Madison, Rappahannock	48 min
Aug 10, 4:44 PM EDT	Severe Thunderstorm Warning	LWX	Fauquier	19 min
Aug 10, 5:05 PM EDT	Severe Thunderstorm Warning	LWX	Nelson	40 min
Aug 10, 5:08 PM EDT	Severe Thunderstorm Warning	LWX	Fairfax	18 min
Aug 10, 5:09 PM EDT	Special Marine Warning	LWX		96 min
Aug 10, 5:12 PM EDT	Severe Thunderstorm Warning	LWX	Arlington, Fairfax, City of Alexandria, City of Fairfax, City of Falls Church	48 min
Aug 10, 5:16 PM EDT	Severe Thunderstorm Warning	LWX	Clarke, Fauquier, Loudoun	44 min
Aug 10, 5:53 PM EDT	Severe Thunderstorm Warning	LWX	Arlington, Fairfax, City of Alexandria	29 min
Aug 10, 6:31 PM EDT	Special Marine Warning	LWX		64 min
Aug 10, 6:35 PM EDT	Special Marine Warning	LWX		85 min
Aug 10, 6:50 PM EDT	Special Marine Warning	LWX		85 min
Aug 10, 6:53 PM EDT	Special Marine Warning	LWX		69 min
Aug 10, 7:32 PM EDT	Special Marine Warning	LWX		88 min

Nearby

Severe Thunderstorm Warnings in Virginia, 2021 Every severe thunderstorm warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.